#只需发送一次的AT
only_once = ['AT+SAPBR=3,1,"CONTYPE","GPRS"'
    , 'AT+SAPBR=3,1,"APN",""'
    , "AT+SAPBR=1,1"
    , 'AT+MIPSTART="lbsmqtt.airm2m.com",1884'
    , 'AT+MCONNECT=1,60']
